The Wistar Institute group has established a large panel of hybridomas secreting antimelanoma monoclonal antibodies. The first set of antibodies was used by all groups involved in a Melanoma Workshop organized by NCI. The antimelanoma monoclonal antibodies are at present used for the study of the expression of antigens by premalignant lesions in situ and in tissue culture and for the cytodiagnostic approaches in using an immunoperoxidase assay on fresh-frozen and fixed tissues of primary and metastatic melanoma. IgG2a antitumor antibodies are used for studies of the mechanisms of tumor cells by murine and human effector cells. Monoclonal antibodies are also used in the attempts to develop methods useful in serodiagnosis, nuclear imaging and immunoradiotherapy. Monoclonal antimelanoma antibodies are also used for the construction of immunotoxins in collaboration with Dr. John Collier (UCLA).